Edge connectors are employed to achieve electrical connection to the conductive portion along an edge of a printed circuit card. More particularly, the card may include an array of circuitry printed or otherwise disposed thereon. The various circuits will terminate along one edge at exposed generally equally spaced conductive portions. Circuit cards have been miniaturized in recent years, and in many currently employed circuit cards the conductive strips disposed along the edge thereof are at 0.050 inch center to center spacings.
The edge connector comprises a housing constructed to mount on a printed circuit board, panel or other such structure, and having a slot for receiving the edge of the circuit card that has the conductive portions equally spaced therealong. A plurality of terminals are securely mounted in the edge connector housing at spacings that substantially correspond to the spacings of the conductive portions along the edge of the circuit card. More particularly, the terminals are mounted in the housing of the edge connector to make electrical contact with the conductive portions of the circuit card upon insertion of the circuit card into the slot of the edge connector housing. Each terminal will further include structure for achieving electrical connection to other circuitry on the printed circuit board, panel or other structure to which the edge connector housing is mounted. For example, each terminal mounted in the edge connector may comprise a solder tail which can be soldered to conductive strips on a printed circuit board to which the edge connector housing is mounted.
The prior art edge connectors have largely relied upon terminals which are either force fit or lockingly retained in the housing of the edge connector. For example, the prior art terminals of an edge connector may include members that are resiliently disposed in spaced relationship to one another. As this prior art terminal is urged into a cavity of the edge connector, the spaced apart members of the terminal are urged toward one another and exert a resilient biasing force against walls of the edge connector housing to retain the terminal therein. Other prior art edge connector terminals are constructed with resilient latch members that are adapted to engage an externally disposed wall of the housing to lockingly retain the edge connector terminal therein. Still other prior art edge connectors include combinations of these structures such that a latch mechanism will determine the longitudinal position of a terminal in an edge connector housing, and such that the resilient force fitting of two spaced apart members of the terminal will substantially prevent movement of the terminal within the housing.
One example of a prior art edge connector and a terminal therefore is shown in U.S. Pat. No. 4,558,912 which issued to Coller et al. on Dec. 17, 1985. The terminal shown in the edge connector of U.S. Pat. No. 4,558,912 includes a resiliently deflectable latch member which lockingly engages a ledge adjacent an outer wall of the edge connector housing to align and retain the terminal in the housing. Other edge connector terminals with latch means for lockingly engaging a ledge on an external wall of the housing are shown in: U.S. Pat. No. 4,322,120 which issued to Rilling on Mar. 30, 1982; U.S. Pat. No. 3,731,259, which issued to Occhipinti on May 1, 1973; and U.S. Pat. No. 3,421,136 which issued to Bowley et al on Jan. 7, 1969. Certain of the edge connectors and terminals shown in these references also rely to some extent upon the force fit engagement of the terminals in the electrical connector housing.
One edge connector terminal that relies substantially more on the force fit positioning of the terminal in the housing is shown in U.S. Pat. No. 3,400,360 which issued to Schmitt et al. on Sept. 3, 1968. In the Schmitt reference, the edge connector terminal is biasingly retained in the edge connector housing by resiliently deflecting a pair of cantilevered arms between opposed external walls of the edge connector housing. A similar force fit retention of an edge connector terminal in its housing is shown in U.S. Pat. No. 4,619,495 which issued to Sochor on Oct. 28, 1986 and which relies upon the forces exerted on the external walls of the edge connector housing by the cantilevered contact arms of the respective terminals. Still another similar force fit arrangement of an edge connector terminal in its housing is shown in U.S. Pat. No. 3,543,226 which issued to LaBoue on Nov. 24, 1970.
Other edge connectors that rely upon a complex inter-engagement of terminals within the respective housings are shown in U.S. Pat. No. 3,868,166 which issued to Ammon on Feb. 25, 1975 and in U.S. Pat. No. 4,026,014 which issued to Sugimoto et al on May 31, 1977.
The above-described prior art is considered undesirable in several important respects. First, it has been found that the forces exerted by closely spaced terminals (e.g., 0.050 inch spacings) on the external walls of the edge connector housing can cause the housing to bow. The bowing of the housing in response to outward forces exerted by the closely spaced terminals typically causes a loose mounting of the terminals disposed intermediate the opposed longitudinal ends of the edge connector housing. This loose mounting of centrally disposed terminals in the prior art edge connector housing can result in poor electrical connection to conductive portions of the card inserted therein.
The known edge connectors that do not rely on either a latched engagement of the terminals therein or a force fit engagement of the terminals therein also provide relatively imprecise positioning of the terminals relative to the card inserted therein. Thus, certain of these prior art terminals may make poor electrical contact with conductive portions of the card, particularly if those conductive portions are small and closely spaced.
One particularly effective edge connector is shown in co-pending U.S. patent application Ser. No. 046,375, entitled "DOUBLE SIDED EDGE CONNECTOR" which was filed by Paul L. Rishworth and Alan S. Walse on May 4, 1987, and which is assigned to the assignee of the subject invention. The edge connector of U.S. patent application Ser. No. 046,375 is particularly effective for circuit cards having closely spaced conductive portions thereon. The edge connector shown in the co-pending application includes a housing formed from hermaphroditic housing halves with terminals heat staked in their respective housing halves prior to assembly of the housing halves to one another. The heat staking of the terminals to their respective housing halves ensures precise alignment of the terminals without the complex and undesirable force fitting and latching which had been employed in the above-described prior art. Although the edge connector shown in the above-described co-pending application has proved particularly effective, it is often desirable to provide an edge connector with a unitary housing and without the requirement of heat staking or otherwise securing the terminals to the housing.
In view of the above, it is an object of the subject invention to provide an edge connector for achieving effective electrical connection to a circuit card having closely spaced conductive portions thereon.
It is another object of the subject invention to provide an edge connector having a unitarily molded housing with closely spaced electrical terminals securely mounted therein.
It is an additional object of the subject invention to provide an edge connector where the terminals therein do not significantly bow the walls of the edge connector housing.
Still a further object of the subject invention is to provide a terminal for an edge connector that achieves secure mounting in the edge connector housing and that achieves superior electrical contact with the conductive portions of a circuit card.